* do-file for Supplementary Exercise 11.15-17 of IPS7e
version 17 /* works also with versions 13-16 */

import delimited "R:\Chapter 11\ex11_015.csv"


* 11.15
pwcorr gpa iq age sc c1 c2 c3 c4 c5 c6, sig
regress gpa iq


* 11.16
regress gpa iq c3
regress gpa iq sc c3


* 11.17
regress gpa iq c1 c5
predict fit, xb
predict stdres, rstandard
qnorm stdres
scatter stdres fit
swilk stdres

* analysis without outlier
drop if stdres<-4
regress gpa iq c1 c5
capture drop fit stdres
predict fit, xb
predict stdres, rstandard
scatter stdres fit
qnorm stdres
swilk stdres